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Traxxas Now with More Horsepower

April 9, 2010 Leave a comment

Okay, perhaps the title is a bit misleading…more computational horsepower. Today, I finally got around to mounting the TS-7800 from Technologic Systems. It’ll be running all the main processing and communicating with the micro controller via a serial port.

Additionally, we’d failed to include a shiny “GO” switch anywhere in the system so I used the DIO port on the ARM to read in a signal to indicate the mission should execute. If you are looking for sample code for the TS-7800, Eric Robishaw’s example is a good start.

If that’s a little much to parse, here’s my simpler variant. It does far less but is a test bit of code that shows the reading without a lot of extra capability.

I’ll leave you now to get back to porting code over to the board. Here’s the vehicle with its ever growing payload.

Computational Horsepower for Easy Living

Update: Just a word of warning, the distribution of Debian shipped with these board is ANCIENT. Packages are no longer available.

Vehicle Overview and Near Destruction

April 1, 2010 Leave a comment

Just for fun

And some near destruction before proper handling of GPS popping was in place…

Apparently my code has a preconceived need to heard toward fences. Don’t ask me why….

Categories: General, Hardware, Platform, Sensors

Race Day Vehicle Ready for Duty

March 21, 2010 1 comment

Our race day vehicle is finally ready for some action.  Here are some pics:

After two weeks of battling the speed control, the Traxxas Slash is ready.  It has 4 stationary IR range finders, one scanning IR range finder, a compass, a GPS, and a wheel encoder.

X-Bee Madness

March 17, 2010 Leave a comment

We’ve using X-Bee modules to send information and commands between the vehicle and a laptop. After we added all the sensor information and other feedback to Proto-2, I started to see communication drop outs when attempting bi-directional comm. Since it is a stop-gap mechanism for test and debug, I wasn’t too worried about it but wow has it been annoying.

The modules are the X-Bee 900 Pro‘s. We had the baud rate ramped up to 115.2 but decided after some calculations to drop back to 38400. No help. So I dug through the manual again. Likely, we should be using API mode but for the moment we kept it simple and just left them in the default broadcast configuration.

The downside of this mode is that the modules are not really communicating point to point even though only two are in the system. So they duplicate broadcast messages to help assure the messages get to everyone in the message. The default duplication is set to 3. I lowered it to 1. If we drop a message here or there, it shouldn’t really effect the performance of the system significantly.

Also, the vehicle is really and end-point, not a router and will never be for this configuration so I changed it to be an end-point not a router. However, that required a firmware upgrade which was seamless using the X-CTU software other than it defaulting the module back to 9600 baud. Honestly both could be set as endpoints I think but I didn’t test that configuration since I was in a rush to get the comm working.

I also tried lowering the packet ratio to zero prior to the other changes to immediately transmit characters rather than bundling messages. It proved too not help but might be a good option at some point. I also lowered the XOFF buffer maximum to 128 characters down from the default of 319 since none of our message strings exceed that length.

If we were going to rely on the radios for good communication, the API interface is the way to go not the transparent default. The changes cleared up the congestion but I made mass changes so cannot specify precisely which one did the trick. If you run into similar issues, I can check the exact configuration and setting changes.

In the end, one more hurdle cleared.

Fuzzy Picture Day

March 12, 2010 Leave a comment

Managed to quickly get the new encoder installed on the Traxxas vehicle over lunch today. I only had my cell phone camera with me and the results indicate how well I can manage to take shots with it. I am completely unable to hold it still enough for close-up shots.

We managed to get the encoder mounted. Floyd constructed a few cables while I was fabricating the bracket. The GPS was also replaced on the Traxxas. Someday I’ll remember everything I need to check on a data sheet before ordering. No worries. Who cannot use a few extra bits?

Encoder is the fuzzy object left of the right wheel.

Floyd 'The Man' crimping pins.

Prototype 2 up and running!

March 6, 2010 2 comments

I just finished the initial software and hardware for Prototype Number 2.  It is based on an RC Tahoe from New Bright.  This prototype contains all of the sensors we will be using in the contest and could be used as a backup is needed (albeit much slower and a much rougher ride).

Fab Nearly Finished

February 28, 2010 Leave a comment

Everything barring the encoder has been installed on the new vehicle. I’ll get more photos up after the fabrication is completed and after final electronics integration.

Hinged Plate for Electronics

Servo for Panning Ultrasonic

GPS Module in the Rear

Categories: General, Hardware, Sensors